In roller doors with a flexible door leaf and with a winding roller for the door leaf, mounted rotatably above the door opening, there has to be provided means for compesating the weight of the door leaf and tensioning means acting on the lower end of the door leaf to tauten the door leaf.
Weight compensation means alone can be provided in a very simple manner, by a drum on one or both sides, connected with the winding roller, rotating integrally therewith and on or from which a traction member winds up or down, in contrary direction to the door leaf on the winding roller, the traction member being loaded with the counterweight to the door leaf. The counterweight can also be suspended on the traction member by means of an idle roller, and the end of the traction member may be connected with the lintel of the door opening (CH-PS 89 785).
For tautening the door leaf it is known to guide the traction member, on which the counterweight is suspended by means of an idle roller, via a guide roller which is mounted rotatably on the lintel of the door opening and via another guide roller which is mounted at the base of the door opening, and to connect said traction member with the door leaf or with a strip which reinforces the lower edge of the door leaf. By way of the limbs of the traction member which run from the idle roller, the weight which is suspended on the idle roller acts on the one hand as the traction force which tautens the door leaf, and on the other hand, via the drum of the traction member, with a torque which is dependent upon the torque which is exerted by the door leaf, with the particular winding radius in question, on the winding roller (DE-PS 23, 41 328). The arrangement of one loose roller on each of the two sides, at the height of the door opening, with a deflection roller at the lintel and a further deflection roller at the base of the door opening, replaces the one loose roller provided in another known arrangement (U.S. Pat. No. 262,398) which is arranged underfloor and pulled downwards by resilient force, and removes the disadvantage which the underfloor arrangement of the roller entails. Irrespective of the arrangement of the loose roller at the height of the door opening or underfloor, and whether or not a weight loading or spring loading of the loose roller is provided, it is difficult to balance out the weight of the door leaf. In U.S. Pat. No. 262,398 the drum for the traction member is of conical shape and has a screw thread for guiding the traction member, whereby in each case the corresponding winding diameter of the door leaf on the coil of the winding-up roller corresponds to the of the traction member on the drum, so that the tensioning roller does not have to balance-out any noteworthy differences of the free length of the traction member. In particular when flat belts are used as traction members because of their long life, there is no possibility of a helical winding because of the drum width thereby occasioned. During the winding of the traction member in layers one over the other--which takes place with inverted tendency in relation to that in the winding of the door leaf--corresponding length-differences have to be balanced out, with corresponding dimensioning of the tensioning device. In so far as comparatively large differences of length have to be compensated, otherwise a free roller which is under weight force or spring force is used or else a constructionally expensive winding device is used, so that therefore it is partially necessary to have a further deflection of the traction member over a fixed roller, to the height of the drop of the door, and a long traction member is necessary, (European patent specification 0276045).
According to German Utility Model 82 06 622, there is additionally provided a spring which is arranged in the winding roller, and which becomes tensioned when the door leaf is being wound up, and which is intended to act simultaneously as a safety device to prevent the door leaf from dropping down. The arrangement of the spring in the winding roller, however, is constructionally expensive and makes maintenance more difficult.
U.S. Pat. No. 3,460,602 discloses a roller door without weight compensation, in which the door leaf is tensioned by springs housed in the door leaf at its foot and connected to traction members wound on the door shaft, extending downwards to guide pulleys and then up to the springs. In this construction the travel of the door leaf and/or the tensioning means are severely restricted.
In German patents 32 45 009, 33 45 016, the weight compensation device and the device for tautening the door leaf were separated from one another, without the constructional expenditure having been reduced and without maintenance having been rendered easier.
An object of the invention is to obtain a robust construction and easier maintenance for the door leaf tautening means, whilst separating the functions of weight compensation and tautening of the door leaf.